Each member is a link to their profile (I think) you have to change the link colors in admin options to change the colors. Or you can change them with css.
strActiveMemberList = strActiveMemberList & "<font color=""" & strForumFontColor & """ class=""your class"">"
if rsAM("M_LEVEL") = 2 then
strActiveMemberList = strActiveMemberList & "<font color=""" & strAUModColor & """>"
elseif rsAM("M_LEVEL") = 3 then
strActiveMemberList = strActiveMemberList & "<font color=""" & strAUAdminColor & """>"
and in inc_header
".your class a:link {color:your color;}" & vbNewLine & _
".your class a:visited {color:your color;}" & vbNewLine & _
".your class a:hover {color:your color;}" & vbNewLine & _
".your class a:active {color:your color;}" & vbNewLine & _
edit-- I miss read 
It seems there is no color defined
find these lines in inc_activeusers and add the part in red
if strAUPCollapse="0" or request.cookies(strUniqueID & "HideActiveUsers") = "N" or request.cookies(strUniqueID & "HideActiveUsers") = "" then
response.write " <tr>" & VBNewLine & _
" <td bgcolor=""" & strForumCellColor & """ rowspan=""2"" width=""10px"">" & VBNewLine & _
" " & getCurrentIcon(strIconGroup,"","") & VBNewLine & _
" </td>" & VBNewLine & _
" <td bgcolor=""" & strForumCellColor & """ colspan=""" & sGetColspan(6,5) & """>" & VBNewLine & _
" <font color=""" & strForumFontFace & """ face=""" & strDefaultFontFace & """ size=""" & strFooterFontSize & """>" & VBNewLine & _
" " & fLang(strLangMOD_Ls3kAU_00010) & ": " & intActiveMembers & " | " & VBNewLine
if strAUAnon and not(bolOverride) then
---end edit